Odor improvement of petroleum oils



Patented Mar. 2, 1 954 UNITED PATENT OFFICE OD'OR'WIPROVEMENT OFPETRYOTJEU'M'DIIZS Russell H. Brown, Hammond, Iildq' 'assig'n'or to Standard Oil Company, Ghicago; IlLga-corporation of Indiana No Drawing pplicatio'n June 30,1951, Serial No. 234,686

This invention relates to the refining or petroleuin oils. 'More particularly the invention relates to the improvement of the odor 'ofpetroleum oils which are substantiallymercaptan free. Still more particularly, the inventionrelates to theremoval of West Texas odor from .petroleurnoils.

Virtually all oils obtained by the distillation of crude petroleum possess a sour odor caused by the presence of mercaptans. In addition to this sour odor, petroleum odors possess a characteristic naphtha odor. Until the discovery of the very-high sulfur crudes, particularly :West Texas crudes, these two odors were the only problems facing the petroleum-refiner. West 'Texas crude, and in particular, the fraction from West Texas crude boiling in the heater oil range, 1. e. about 350 to about 575 F.,- possesses a pungent odor distinctly different from either the sour odor of nfercaptansor the naphtha-type odor normally present in'petroleum oils. Since this-odor was first noticed inand'is'mostprominentin West Texas crude, this particmarodor has been desighated as West Texas odor or W.-T.'-odor. The sour odor of -mercaptans-canbe eliminated by any-one of the numerous'sweetening processes: these processes either-physicallyremovethe rriercaptansfrom the oil -or'--che'mically convert the mercaptansto disulfides which -possess an inoffensive odor. The naphtha odor is not considered as objectionable by the consumer oi -petroleum products. The West'Texas -o'dor' is -'very=objectiona-ble to the consuming-public and saIes-bf heater oils from West Texas crude--ha-'ve--lai'e'en markedly affected by the presence of West Texas odor. Anobj'e'ct 'of'this invention'is toel-im nateiwest Texa'so'dor from petroleum oils. Another object is'to eliminate West Texas odor from petroleum oils "that are substantially 'mercaptan free. I have discovered that the so -called'We's'tTexas odor characteristic-"of certain high sulfur crude petroleum is caused by saturated cyclic --sul-f-ur compounds wherein the "sulfur is {present-within the ring structure. Furthermore, I halved-iscovered that these West Texas odor bodies hombine with mercuric salts to form solid'-oil-i r'1'soliibl'e complexes which can be readily separated {from the on. 'By-contacting an oil characterized *bya West Texas odor, Withanefiectivean'iduiit of "a mercuric salt, such as mercuric chloride, Ther curic acetate, mercuric nitrate, etc, an oil can be obtained thathas the same odor as the acceptable oils from Mid continent, crude. "-A-sour'oil can besweetened by treatment wit mercuric salts such as mercuric chlofideaasiner-z Y sonims. (c1. 196 30) high molecular weight mereaptans to'-=foi m*'0il"- 2 captains dea'ct to form g neraliy inseiume mer capti'des. Howeverwwhe sweetening oils bellies above the gasoline range, such as heater furnace oil; kerosene, the mercury "reacts soluble mercaptides. These oil soluble "mercury mercaptides remain in the sweet oil-and very'aaversely affect the-color stability 'of the "sweet oil; therefore, even though the expense of'swe'e'te'n'ing with mercury salts were to be 'disreg'arded, sweet ening of sour oils boiling abovethegasoline:range with mercurysalts is not desirable.

The cyclic sulfides which cause the West Texas odor are not affected 'by the usua'l sweetening processes; neither the merc'aptan removal ,processes nor the mercaptanconversion'processes.

In the usual 'mercaptan removal z-prc'c'esses I include the following: caustic met'hanol process for the extraction of merc'aptans. socalled "solutizer processes wherein the mercaptans are removed from the sour oilby extraction with aqueous alkali'solutioncontaining iner captan solubility promoters "such potassium isobutyr'ic acid, phenolic compounds su'ch as those derived-"by'c'austic Washing from cracked-- oils,

wood tars, etc. In the usual mercaptan *conversion pr'ocesses I include the following: The so called copper chloride-sweetening process. The :p'rocess 'wherein the sour oilis "contacted with aqueous alkali at elevated temperatures inthep-resence of air. The processwherinsour' on is 'c'o'il'tel'itied"vvith aqueous alkali at abou'tlOO FI'iri the presence of an oiiidation catalyst'such as copper suliatein the presence of air. "Thefprocess wherein the sour oil is contacted with a very small amount of alcohol, about '1'%, and a concentrated aqueous alkaline solution in the presence o'ffia'ir. The conventional doctor process wherein the sour oil is contacted with aqueous sodium plumbite.

Merca-ptans can he 'removedrrom-sour oil by sulfuric *acid orphosphoric acidtreating. T '1 are found that asouroil'containing West'Texas r bodies can be sweetened-by acid treatin'gflirit t appreciable simultaneous improvem'eriv in t-he West Texas odor. Thus a West Texas-heater 011 was treatedwithas much as 10"'Ibs. of 98% sulfuric'acidjper barrel of heater b'il Withoutddmmercially satisfactory improvement in West Texas odor characteristic; this treatment is in excess of theaci'd usagdnetdedfor producing a sweet oil. However,anincrease in theamountof 98% sulfuric acid usage above lo lbsr resulted in animprovement in WestTexas odor properties. u-i'm oi-l equivalentito heaten oilv in odor quality was produced when the West Texas heater oil was treated with about 15 lbs. of sulfuric acid per barrel of oil. Thus I mean to include among my usual sweetening processes the treatment of a sour oil with sulfuric acid in such amounts that a sweet oil is produced with little or no improvement in West Texas odor.

The mercuric salt can be added to the West Texas odor body containing substantially mercaptan-free oil in various ways. For example, in the form of mercuric salt-feed oil slurry; in the form of a concentrated mercuric salt-water solution; in the form of a mercuric salt-alcohol solution, aqueous alcohol can also be used. The solid mercuric salt can be dispersed into the feed oil directly. I prefer to use a saturated aqueous solution of the mercuric salt.

Contacting can be carried out in any of the numerous ways known to the art. Some of these methods are agitation in a tank, injection of the treating agent into a line and passing the material through an orifice mixer or a centrifugal pump.

The mercuric salt-odor-body complex is a pasty solid of very low solubility in oil. This solid can be removed from the oil by a settling period or by filtration.

I have found that, in order to obtain substantially complete removal of the West Texas odor bodies, it is necessary to add from about 1 mol to about 3 mols of mecuric salt per mol of the cyclic sulfide compound present in the oil. A trace of the mercuric salt remains in the treated oil even after prolonged settling. This trace of mercuric salt can be removed from the oil by washing with an aqueous sodium sulfide solution. However, this washing procedure may be dispensed with if a metal deactivator is added to the oil in order to counteract the deleterious effect of the mercury on the color stability of the oil. A suitable metal deactivator is N,N disalicylidine-1,2-diaminopropane. In general between about 0.0002001 wt. per cent of the metal deactivator should be added. A preferred amount is 2 lbs. per 1,000 barrels of oil, i. e. about 0.001 wt. per cent.

The West Texas odor bodies removed by the treatment of the West Texas oil with mercuric chloride are liquids with an extremely disagreeable odor and have the following characteristics:

ASTM distillation, "F 330-565 A study of these West Texas odor bodies indicates that the structural formula for the individual compounds falls into one of the types listed below, where R can be either an alkyl radical or hydrogen.

ODOR EVALUATION PROCEDURE The first step in the attack on the West Texas odor problem was the development of a standard odor evaluation (level) procedure. A set of standards was prepared as follows: A repre sentative sample of a West Texas heater oil which had been sweetened by the doctor process was obtained. Various amounts of the standard West Texas heater oil were added to a medicinal white oil (U. S. P. grade). It was found that a small quantity of odoriferous oil added to a large quantity of virtually odorless medicinal white oil permitted fine distinctions to be made between diiferent samples of oils containing West Texas odor bodies. The West Texas odor value and the composition of the standard are given below:

Sweet West Medicinal West Texas Odor Value Texas Heater White 011 Oil (1111.) (ml.)

8.6 491. 4 l1. 5 488. 7 14. 2 485. 8 17. l 482. 9 20.0 480. O 22. 9 177. 1 25. 8 474. 2

The odor evaluation procedure is as follows: 20 ml. of the unknown oil are added to 480 ml. of the standard medicinal white oil. This diluted unknown oil is then compared with the odor standards by each of twelve sensitive and experienced individuals and assigned a West Texas odor number by each of them. It has been found that quite accurate reproducibility is obtainable. The average of the twelve odor values is taken as the West Texas odor value of the particular unknown oil. After a little practice, the odor panel can check an unknown within :1 odor number.

Run 1 An M. C. heater oil with a boiling range of 350 F. to 575 F. was doctor sweetened to pro-v duce a substantially mercaptan-free oil. This sweet M. C. heater oil had a West Texas odor number of 16 and is not objectionable in odor to consumers. A 250 ml. portion of this oil was contacted for 2 hours with 25 ml. of saturated aqueous mercuric chloride solution (about 7 grams of mercuric chloride per ml. of water). The water layer was withdrawn and the treated oil was washed with a sodium sulfide solution to remove entrained mercuric chloride. The mer curic chloride treated oil had a West Texas odor number of 16, showing no improvement with mercuric chloride treatment.

Run 2 A West Texas heater oil of about 350 to 575 F. boiling range was doctor sweetened to produce a substantially mercaptan-free sweet oil. The sweet West Texas oil had a total sulfur content of 0.70wt. per cent anda West Texas odor number of 36. A 250 ml. sample of this oil was treated with mercuric chloride as shown in Run 1. The treated oil had a West Texas odor number of 14. The loss of material in this treatment was slightly less than 0.1 volume per cent. The sulfur content of the West Texas odor-free sweet oil was 0.68. Thus by removing only 0.1 volume per cent of the feed oil, a heater oil having an odor better than the generally acceptable M. C. oil was obtained.

Run 3 The experiment of Run 2 was repeated'using aqueous mercuric chloride and a 30-minute contact time. The treated oil had a West Texas odor number of 16. r

Run 4 A 250 ml. portion of doctor sweet West Texas heater oil was treated with ml. of a solution of mercuric chloride in aqueous methanol; the contacting time was hour. The treated oil from this run had a West Texas odor number of 15.

I have found that my process is not appreciably affected by the temperature of contacting. I prefer to operate at temperatures lower than the decomposition temperature of the disulfides present in the sweet oil, about 350 to 400 F. My preferred operating temperature is at ambient temperatures, i. e. between about 60 and about 100 F.

Briefly, my process comprises the treatment of a petroleum oil which is substantially mercaptanfree and contains West Texas odor bodies, with a mercuric salt in an amount suflicient to produce a final oil of the desired West Texas odor level, separating the oil-insoluble odor-body-mercuric salt complex from the treated oil and, if desired, adding an effective amount of a metal deactivator to the treated oil.

I claim:

1. A combination process for the elimination of mercaptans and cyclic-sulfides from a petroleum oil containing appreciable amounts of these organic-sulfur compounds, which process comprises (l) treating said oil under conditions wherein essentially only mercaptans are eliminated from said oil, (2) contacting said treated oil from (1) with a mercuric salt, in an amount of between about 1 and about 3 mols per mol of cyclic-sulfides in said treated oil, and ('3) separating an oil-insoluble mercury salt-cyclic-sulfide complex from an essentially cyclic-sulfide-free oil.

2. The process of claim 1 wherein said oil is a high sulfur heater oil boiling between about 350 and 650 F.

3. The process of claim 1 wherein said mercuric salt is mercuric chloride.

4. A combination process for the removal of odors from petroleum oils boiling between about 350 and 650 F. caused by the presence of mercaptans and cyclic-sulfides, which process comprises (1) doctor sweetening said oil to produce a sweet oil containing cyclic-sulfides, (2) contacting said sweet oil with an aqueous mercuric salt solution in an amount of between about 1 and about 3 mols of salt per mol of cyclic sulfide in said sweet oil, (3) separating a cyclic-sulfide containing solid from an essentially cyclic-sulfide-free oil and (4) stabilizing the oil from (3) by dissolving therein an effective amount of a metal deactivator.

5. A combination process for the removal of odors from high sulfur petroleum oils boiling between about 350 and 650 E, which odors are caused by the presence of mercaptans and cyclicsulfides, which process comprises (1) treating said oil wtih about 10 lbs. of about 98% sulfuric acid per barrel of said oil, (2) separating acid sludge from treated oil, (3) contacting said treated oil with aqueous alkali metal hydroxide solution, (4) separating a sweet oil containing cyclic-sulfides from aqueous solution, (5) contacting said sweet oil with an aqueous mercuric chloride solution containing between about 1 and about 3 mols of mercuric chloride per mol of cyclic-sulfide in said sweet oil, (6) separating a cyclic-sulfide-free oil from a cyclic-sulfide containing complex, and (7) adding an effective amount of a metal deactivator to the oil of (6).

RUSSELL H. BROWN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,771,350 Ramage July 22, 1930 1,954,887 Morrell Apr. 7, 1934 1,963,556 Morrell June 19, 1934 1,980,555 Schulze Nov. 13, 1934 2,221, 83 Dolbear Nov. 12, 1940 OTHER REFERENCES U. S. Bureau of Mines-Report of Investigations 4060, December 1946. 

1. A COMBINATION PROCESS FOR THE ELIMINATION OF MERCAPTANS AND CYCLIC-SULFIDES FROM A PETROLEUM OIL CONTAINING APPRECIABLE AMOUNTS OF THESE ORGANIC-SULFUR COMPOUNDS, WHICH PROCESS COMPRISES (1) TREATING SAID OIL UNDER CONDITIONS WHEREIN ESSENTIALLY ONLY MERCAPTANS ARE ELIMINATED FROM SAID OIL, (2) CONTACTING SAID TREATED OIL FROM (1) WITH A MERCURIC SALT, IN AN AMOUNT OF BETWEEN ABOUT 1 AND ABOUT 3 MOLS PER MOL OF CYCLIC-SULFIDES IN SAID TREATED OIL, AND (3) SEPARATING AN OIL-INSOLUBLE MERCYRY SALT-CYCLIC-SULFIDE COMPLES FROM AN ASSEMBLY CYCLIC-SULFIDE-FREE OIL. 